Rubber insulated electrical conductor



Nov. 28, 1933, H. D. RICE 1,93 994 RUBBER INSULATED ELECTRICAL CONDUCTORFiled Aug. 5, 1931 INV ENTOR HAROLD 0. RIC

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"Nrrso STA Al'EN'l orrice masses RUBBER WSULATED ELECTRICAL CGN'DUCTDRHarold D. Rice, Bristol, R. IL, assignor to National India LubberCompany, Bristol, R. L,

a corporation of Rhode Island Application August 5, 1931. Serial No.555,209

' eclaimo. (01.173-264) This invention relates to, rubber insulatedelectrical conductors and methods oi. manufacturing the same.

This is a continuation, as to all common subject matter therein, 01'application No. 388,036

filed August 23, 1929.

Heretofore it has been the practice to apply rubber insulation toelectrical conductors byv either extruding the rubber onto theconductor,

or by forming the rubber in sheet form, cutting the sheets intostrips-and wrapping the strips,

up in parallel, or twisting, with or without a braid, and finallycovering if desired with silk, rayon, or cotton braids, or the like, orreinsu= lating with a rubber compound.

It is the object of this invention to provide a rubber insulation forconductors which is or" a 5 grainless texture, is unmilled, and which istough, flexible, durable and has a high resistance to abrasion.

It is also the object of this invention to apply a suitable rubberinsulation to a conductor directly from latex or other aqueousdispersions of rubber.

I It is the further object of this invention to provide an insulationfor an electrical conductor from an aqueous dispersion of rubber thathas high electrical insulating properties especially when wet.

It is also the object of the invention to pro vide improvedconstructions of various types of electrical conductors. V

Uther objects and advantages of. the present invention will appear frontthe following description.

In the drawing is shown various embodiments of the invention; in whichFigure 1 illustrates a solid conductor, insulated, and braided single;

Fig. 2 illustrates a stranded conductor, insu lated, layed up .inparallel, and braided double;

Fig. 3 illustrates another construction stranded conductor; insulated,layed up in parallel, and braided double;

Fig. 4 illustrates an insulated solid conductor such as code wire;

5 Fig. 5 illustrates a stranded conductor, insulated, twisted double,and with an overall reinsulation of rubber; and

Fig. 6 illustrates a stranded conductor, insulated, twisted double witha filler, and with an overall reinsulation of rubber.

The conductor to be insulated is brought to size on wire drawingmachinery if a solid con-. ductor, or made in stranded form if of aflexible construction, in a manner well known in the art. Theconductormay be tinned, paper wrapped, or provided with a serving ofcotton or other fibrous material prior to the application of the rubberinsulation thereon. Such a covering, as is well known, protects the wirefrom the action 'of free sulphur contained in the rubber compositionwhich otherwise would migrate into contact with the copper of'the wireto produce an undesirable reaction.

The conductor preferably tinned, or served with cotton or other fibrousmaterial, or both it tinned and served with fibrous material may then beconducted into and through a bath of aqueous dispersion of rubber whichpreferably takes the form of la ex which. has been purified andcompounded mitt; lca'nizing ingredients and if desired also filleringredients. As the con duster emerges from the coating bath, it is pref'erably passed through a drying chamber to co= need be employed and thevulcanization may be completed by a subsequent heating operation. $5 Therubber in the disperson may, if desired, be in vulcanized condition, andin such case, a low or temperature and smaller drying chamber may beused than when vulcanization is also effected. The dipping and dryingo'r dipping and coagulat= ing operations may be repeated untila-sumcient thickness of rubber has been formed on the who to provides.layer having the desired electrical insulation properties.

in Figures 1 and 2 are illustrated examples of conductors made accordingto the present in vention. Figure 1 illustrates a conductor in which 1represents a solid core, 2 a cottonservlug there over, 3 a layer ofrubber deposited from an aqua out dispersion of rubber over-the serving,and a 11 a rlnal braid over the insulation on the single conductor.Figure 2 illustrates a pair of parallel stranded conductors such as maybe used for lamp cord, in which 5 represents the stranded cores, 6 acotton serving over the cores, '1 a layer of rubber deposited from anaqueous dispersion of rubber over the serving, and 8 an overall braidingover the two conductors made of fibrous material, such as cotton orrayon, or the like. Conductors insulated with rubber from an aqueousdispersion of rubber may be finished in a variety of ways. For singleconductors, they may be finished with a braid as shown in Figure 1. Formultiple conductors, a plurality of the rubber insulated wires, eitherwith or without a braid over each wire, may be finished by braidingoverall, as shown in Figure 2.

For still heavier insulations, and where even a greater toughness,durability, and resistance to abrasion is desired, the single conductorsinsulated and braided may again be passed through a rubber dispersionand dried or otherwise coagulated. As before this may be repeated anynumber of times, depending upon the thickness or the layer of insulationdesired. This dipping in the dispersion again after the wire has beencoated with a film of rubber and a braid has been provided over therubber, impregnates the braid and also sufiicient dispersion passesthrough the braid so that on subsequent drying, and vulcanization, thenew film of rubber over the braid is bonded through the braid to theinner rubber film. Such a novel construction of a rubber film over thebraid which also provides a bond with "the inner rubber film through thebraid, provides an exceptional insulation. Conductors formed in thismanner may be finished in the same manner as the conductors with onelayer of rubber insulation above, either by braiding 'i'or singleconductor, or braiding overall a plurality of conductors with or withouta braid over the single wires, or by reinsulating overallwith a rubbercompound. Figure 3 illustrates as one form of such construction a pairof parallel stranded .conductors such as may be used for lampcord, inwhich 9 represents the stranded cores, 10 a cotton serving over thecores, 11 a layer of rubber deposited from an aqueous dispersion ofrubber over the serving, 12 a braid 0t fibrous material, for example,cotton over said film. Over this braid 12 another film 13 of rubberbonded to the first film 11 through the braid 12, is deposited from anaqueous dispersion of rubber, and 14 represents an overall braiding overthe two conductors made or a fibrous material, such as cotton, rayon, orthe like.

Figure 4 illustrates a solid conductor such as code wire in which 15represents the usual tinned solid conductor and 16 a layer of rubberdeposited Irom an aqueous dispersion of rubber over they core.

Figures 5 and 6 illustrate conductors which are twisted in pairs andhave an overall reinsulation of rubber deposited from an aqueousdispersion of rubber. Figure 5 illustrates a pair of twisted strandedconductors in which ll represents the stranded cores, 18 a cottonserving over the cores, 19 a layer of rubber deposited from an aqueousdispersion oi. rubber over the serving and 20 dispersion of rubber overthe serving, 24 a pair of fillers made of twisted cotton threads, 25 acoarse net like overall braid of cotton and 26 an overall reinsulationover the twisted conductors and fillers of rubber deposited from anaqueous dispersion of rubber. 0! course, the reinsulations 20 and 26may, if desired, be tubed, if desired from a solid rubber composition inthe usual manner.

Insulation deposited from normal latex or other aqueous dispersions ofrubber which contain a high percentage of water soluble non-rubberingredients have inferior electrical insulating properties, especiallywhen moist. I have found that a purification of the latex such as areduction of the amount of non-rubber ingredients in the latexcomposition by purification processes such as disclosed and claimed inthe Hopkinson and Gibbons Patent Reissue 16,874, by dialysis orelectrodialysis, or by creaming processes such as with the aid ofcreaming'agents and/or centrifuging provides a latex from whichinsulation may be made which has high electrical insulating properties,even when wet. As an example, I may use a latex twice creamed withpectin or alginates or Irish moss or other suitable creaming agents,forming a creamed latex of 50-60% solids.

Whereas a normal latex contains about 11 or 12% of solid non-rubberconstituents which includes soaps, resins, proteins, salts quebrachitoland smaller amounts of other maerials, and concentrated latex even agreater percentage, a once creamed-latex contains approximately but 4-5%of solid non-rubber constituents and a twice creamed latex contains from2 /2-3% non-rubber constituents, and if the creaming process iscontinued the amount of non-rubber constituents may be even furtherdecreased. On the other hand, the best known types of crude rubber haveanywhere from '7 to 8% solid non-rubber constituents. In order to formthe best electrical insulation from an aqueous dispersion oi. rubber,the amount of solid non-rubber constituents should be kept as low aspossible. The removal of practically all of the water solubleconstituents contained in the latex, as by creaming, renders the rubberdispersion most satisfactory for use in forming rubber insulation.

The following examples of insulation compositions are merely included asillustrations and are not intended to be construed in any way aslimitations of the invention:

Example 1 Parts Rubber as creamed latex 100 Zinc oxide--- 4 Su1phurWhiting Zinc dimethyl amino dithiocarbamate ,5 Ammonium stearate 1Sodium undecylenate (25% solution) 2 Example 2 iii ea set Example 3Parts Rubber as creamed latex Mid Zinc oxide l Sulphur it Zinc dimethylamino dithiocarbamate A Ammonium stearate 1 Examples 1 and 2 illustratelatices creamed once or more times as desired, containing vui canizingingredientsand also filler materials. Example 3 illustrates a latex,creamed once or more times as desired, containing vulcanizingingredients and no compounds other than are necessary for vulcanizationpurposes. The zinc dimethyl amino dithiocarbamate is an accelerator ofvulcanization. The ammonium stearate acts as a stabilizer of thedispersion and increases the penetrating power of the rubber dispersion.and thus enables it better to wet the materials such as the cottonservice etc. with which it comes in contact. The sodium undecylenate inExample 1 is a stabilizer. The various ingredients may be added dry, insolution, or in suspension in a manner well known in the art. Theasphalt in Example 2 is preferably added in the form of an emulsion. Theabove formula: may be cut with water to any desired solids content. Ihave found a latex composition compounded. to about 40% solids contentvery satisfactory to apply. Other accelerators and compolmdingingredients may be used, if desired. The propoi ions and nature of thecompounding ingredients may obviously be varied to suit the purposes towhich the conductor is to be put as will be evident to one skilled inthe art. The latices, as described above, may be purified in other waysthan by creaming, if desired.

While the invention has been described more or less in detail, it is notintended thereby to so limit the invention inasmuch as the examplesherein set forth are merely illustrative thereof and variousmodifications may be made without departing from the invention, thescope of which is indicated in the following claims.

Having thus described my invention, what I.

claim and desire to protect by Letters Patent is:

1. An electrical conductor comprising a core of conducting material andan insulation thereon of vulcanized and srainless unmilled rubbercomposition containing not more than 5% of natural non-rubberconstituents.

2. An electrical conductor comprising a core of conducting material andan insulation thereon oi vulcanized and grainless unmilled rubber.composition substantially free from water-soluble constituents.

3. An electrical conductor comprising a core of conducting material andan insulation there= on of vulcanized and grainless unmilled rubbercomposition substantially free from water-soluble constituents andcontaining not more than 3% natural non-rubber constituents.

4. an electrical conductor comprising a core of conducting material andan insulation there= on oi vulcanized and grainless unmilled rubbercomposition containing not more than 3% natu= ral non-rubberconstituents based on the rubber content.

5. An electrical conductor comprising a core of conducting material. andan. insulation there= on of vulcanized and grainless rubber com-=position deposited directly from a creamed rub ber latex.

d. An electrical conductor comprising a core of conducting material andan insulation there on of vulcanized and grainless rubber composi tiondeposited directly from a rubber latex from which has been removed themajor proportion of natural non-rubber constituents.

"Z. An electrical conductor comprising a core of conducting materialandan insulation thereon of vulcanized and grainless rubber composi tiondeposited directly from rubber latex, said I latex containing not morethan 5% natural nonrubber constituents on a dry rubber basis.

8. An electrical conductor comprising a core of conducting material andan insulation there on of vulcanized and grainless rubber composttiondeposited directly from rubber latex, said latex being substantiallyfree from natural ,watcr soluble constituents.

9.1m electrical conductor comprising a core of conducting material andan insulation there on of vulcanized and grainless rubber composi tiondeposited directly from rubber latex, said latex containing not morethan 3% natural nonrubber constituents on a dry rubber basis and beingsubstantially free from natural water-soluble constituents.

HAROLD D. RICE.

